Gangs, often based in west Africa, trick teenagers into sending intimate pictures of themselves to fraudsters who then threaten to share them with the victim’s family unless they send them money.

Sextortion has been the cause of the deaths of at least two teenagers in recent years. Dinal De Alwis, 16, of south London, took his own life after being blackmailed over nude images.

Murray Dowey, 16, from Dunblane, died shortly after he was targeted by blackmailers. His family told The Guardian they had been “absolutely shattered in the space of a few hours”.

There has been a 19 per cent increase in reports of child sexual abuse material (CSAM) in the the first half of this year as compared with last year, according to the Internet Watch Foundation (IWF).

Tamsin McNally, manager of the IWF’s hotline that lets the public report suspected CSAM, said the rise was probably due to the fact that “perpetrators have become more adept at what they’re doing, they’re widening their nets because they know they can make money”.

She said: “Sextortion is the biggest trend we’ve seen and one of the cruellest. It’s something I see on a daily basis, with reports coming to the hotline internationally as well as from the UK.”

Adam Priestley, a senior manager at the NCA, said extradition was just one option and that agencies may work with other countries to bring perpetrators to justice in their own countries.

“It is the ambition of the NCA to work together with UK and international partners to achieve a judicial outcome”, he said.

“In particular where a young person has died, we strive for a judicial outcome that adequately reflects the severity of the crime. If you offend against people in the UK, this is what happens. You are not safe from prosecution in our country.”